1. Field of the Invention
The invention relates to utility pliers of the self-adjusting type. Such pliers are similar to the channel type but have the capability that, by means of a single-handed manipulation by the user, they will automatically adjust the distance between the gripping jaws in relation to the size of the workpiece to be gripped.
2. Description of the Prior Art
Self-adjusting pliers are disclosed in U.S. Pat. Nos. 4,893,530, 4,802,390, 4,662,252 and 4,651,598. These pliers include two handle members, each having a jaw portion, a neck portion and a handle portion, with the handle members being interconnected at the neck portions and at the handle portions. More specifically, a pawl is fixed to one neck portion and slidably moves in an elongated slot in the other neck portion for engagement with a rack formed in the slot. A coupling link or lever interconnects the handle portions, being pivoted at one end to one handle portion and being slidably movable in a slot in the other handle portion, the coupling link being biased to hold the jaws in a fully open position and to hold the pawl out of engagement with the rack.
When the pliers are used to engage a workpiece, during an initial closing action of the handle members, they will pivot about the pivoted end of the coupling link to close the jaws with the pawl sliding freely along the rack slot. When the jaws engage the workpiece continued closing action of the handle portions will move the pawl into engagement with the rack. This stops the sliding movement of the pawl along the rack slot, and the handle members will then tend to pivot about the pawl. Continued closing action of the handle members will cause the free end of the coupling link to slide in the slot of the adjacent handle portion.
These prior self-adjusting pliers have substantially straight handle portions, and it has been found that, in use, the pawl will not consistently engage with the rack when the jaws engage the workpiece because the handle angles do not permit an alignment of forces suitable for ensuring consistent proper operation. This is particularly true when the pliers are used in an upside down position, i.e., when the pliers are reversed in the user's hand so that the fingers grip the handle member carrying the pawl and the thumb engages the handle member carrying the rack, instead of vice versa. In the case of non-engagement, the handle members will slip relative to one another and the jaws will not firmly hold the workpiece.